JP2023167346A - Optical cable slot, and optical cable - Google Patents

Abstract

To provide an optical cable slot that includes a rib excellent in collapse strength even if being a thin wall, and enabling suppressing undulation upon flexing of an optical cable.SOLUTION: An optical cable slot according to one embodiment of the present disclosure has a plurality of ribs that contains resin of which a flexural modulus is 1000 MPa or more, and is provided in an outer surface in a spiraling way to an axial direction. A ratio h1/t of an average height h1 to an average thickness t in the rib is 4 or more, the rib has a plurality of slits that extends toward a direction from an outer edge part in a longitudinal direction, and a ratio h2/h1 of an average depth h2 of the slit to the average height h1 of the rib is 0.5 or more, and 0.8 or less.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to an optical cable slot and an optical cable.

2. Description of the Related Art Optical cable slots having a plurality of grooves on the outer peripheral surface have been known. Each groove of this optical cable slot accommodates a single optical fiber core, a tape core wire made by bundling a plurality of optical fiber cores with a coating, or the like.

Generally, optical cable slots are formed by profile extrusion using a resin composition such as polyethylene. The optical cable slot has a plurality of ribs erected in an axial direction in a spiral or SZ shape on the outer circumferential surface, and two adjacent ribs among the ribs serve as side surfaces to form a groove.

As such an optical cable slot, one formed using polyethylene, which exhibits excellent surface smoothness and dimensional stability, has been devised (see Patent Document 1).

Japanese Patent Application Publication No. 7-333476

An optical cable slot according to an aspect of the present disclosure contains a resin having a bending elastic modulus of 1000 MPa or more, has a plurality of ribs spirally provided in an axial direction on an outer peripheral surface, and has an average The ratio h1/t of the average height h1 to the thickness t is 4 or more, the rib has a plurality of slits extending in the axial direction from the outer edge in the longitudinal direction, and the average height h1 of the rib is The ratio h2/h1 of the average depth h2 of the slit to the average depth h2 of the slit is 0.5 or more and 0.8 or less.

FIG. 1 is a schematic cross-sectional view of an optical cable according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of an optical cable slot according to an embodiment of the present disclosure. FIG. 3 is a schematic partial perspective view of the rib. FIG. 4 is a schematic partial schematic diagram of a slot for explaining the average height of the ribs. FIG. 5 is a partial schematic diagram of a rib in plan view.

[Problems that this disclosure seeks to solve]
Optical cables are sometimes subjected to external bending during cable routing, so they are required to have crushing strength that can withstand external bending. Furthermore, optical cables used in data centers and the like are required to be capable of transmitting large amounts of data, so it is necessary to increase the density by packing as many optical fibers as possible into an optical cable of a certain diameter. However, when polyethylene, which has been conventionally used as a material for optical cable slots, is used, the crushing strength of the optical cable ribs is insufficient when the ribs are thinned in order to increase the density of optical fibers. On the other hand, when a high-strength material is used as the material for the optical cable slot, flexibility decreases, which causes a problem in that ribs tend to undulate when the optical cable is bent.

The present disclosure has been made based on the above circumstances, and an object of the present disclosure is to provide a slot for an optical cable that has a rib that has excellent crushing strength even if it is thin and can suppress waviness when bending the optical cable. shall be.

[Effects of this disclosure]
The optical cable slot of the present disclosure has a thinner rib, and has excellent crushing strength of the rib and an effect of suppressing waviness when the optical cable is bent.

[Description of embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.

An optical cable slot according to an aspect of the present disclosure contains a resin having a bending elastic modulus of 1000 MPa or more, has a plurality of ribs spirally provided in an axial direction on an outer peripheral surface, and has an average The ratio h1/t of the average height h1 to the thickness t is 4 or more, the rib has a plurality of slits extending in the axial direction from the outer edge in the longitudinal direction, and the average height h1 of the rib is The ratio h2/h1 of the average depth h2 of the slit to the average depth h2 of the slit is 0.5 or more and 0.8 or less.

The optical cable slot (hereinafter also simply referred to as slot) contains resin having a bending modulus of 1000 MPa or more, and thus has excellent crushing strength against bending. Further, by setting the ratio h1/t of the average height h1 to the average thickness t in the rib of the optical cable slot to be 4 or more, the rib can be made thinner. Furthermore, the rib has a plurality of slits extending in the axial direction from the outer edge in the longitudinal direction, and a ratio h2/h1 of an average depth h2 of the slits to an average height h1 of the ribs is 0.5 or more. By being 0.8 or less, appropriate elasticity can be imparted while maintaining the crushing strength of the rib. Therefore, the optical cable slot allows the rib to be made thinner, and is excellent in the crushing strength of the rib and the effect of suppressing waviness when the optical cable is bent. Here, the "flexural modulus" is a value measured in accordance with JIS-K-7171 (2016). In the present disclosure, the "average" in the "average thickness" refers to the average value of thicknesses measured at three arbitrary points. The same applies to "average height," "average width," and "average depth," which will be described later. In the present disclosure, "thin" means that the ratio h1/t of the average height h1 to the average thickness t is 4 or more.

It is preferable that the twisting pitch of the ribs is 600 mm or more and 1600 mm or less. By setting the twisting pitch of the ribs to be 600 mm or more and 1600 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs. The term "rib twisting pitch" refers to the axial interval at which the ribs 2 are twisted in a helical manner and are at the same position in the radial direction of the cross section in the cross section of the optical cable slot.

It is preferable that the average width of the slits is 0.1 mm or more and 20 mm or less. By setting the average width of the slits to be 0.1 mm or more and 20 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs.

It is preferable that the rib has at least one slit per pitch. Since the ribs have at least one slit per pitch, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs.

An optical cable according to another aspect of the present disclosure includes the slot, a tension member embedded in the center of the slot, an optical fiber disposed between the adjacent ribs, and an outer layer covering the slot and the optical fiber. Includes a cover.

Since the optical cable includes the optical cable slot of the present disclosure, the rib in the optical cable slot can be made thinner, and the rib has excellent crushing strength and an effect of suppressing waviness when bending the optical cable.

[Details of embodiments of the present disclosure]
Hereinafter, an optical cable slot and an optical cable according to an embodiment of the present disclosure will be explained in detail with reference to the drawings.

<Optical cable>
As shown in FIG. 1, the optical cable 11 includes an optical cable slot (hereinafter also referred to as slot) 2 having a plurality of ribs 21, a tension member 1 embedded in the center of the slot 2, and an adjacent rib 21. The slot 2 includes an optical fiber 4 disposed between the optical fibers 4 and a jacket 5 covering the slot 2 and the optical fiber 4.

The optical cable 11 may further include an adhesive layer that adheres the tension member and the optical cable slot, and the tension member 1 may be embedded in the optical cable slot 2 via the adhesive layer. The adhesive layer mainly contains an adhesive that bonds the tension member 1 and the optical cable slot 2 together. The adhesive is not particularly limited as long as it can adhere to the tension member 1 and the optical cable slot 2, and thermoplastic resin such as polyethylene can be used. The above-mentioned "main component" means the component with the highest content, for example, the component contained in an amount of 50% by mass or more based on the total mass of the adhesive layer.

<Optical cable slot>
An optical cable slot 2 according to an embodiment of the present disclosure has a tension member 1 buried in the center thereof and has a plurality of ribs spirally provided in the axial direction on the outer peripheral surface. The optical cable slot 2 has a shape in which a plurality of ribs 21 protrude from the peripheral surface of the main body 24 . Further, the central axis of the main body 24 coincides with the central axis of the tension member 1.

The optical cable slot 2 contains a resin having a bending elastic modulus of 1000 MPa or more. If the bending elastic modulus of the optical cable slot 2 is smaller than the lower limit, the optical cable 11 may have insufficient deformability. Further, the upper limit of the bending elastic modulus of the optical cable slot 2 is not particularly limited, but is, for example, 2500 MPa.

Examples of the resin used for the optical cable slot 2 and having a bending modulus of 1000 MPa or more include polyethylene and polypropylene. Among these, polypropylene or high-density polyethylene is preferred from the viewpoint of increasing the crushing strength of the ribs 21.

The lower limit of the content of the resin having a bending elastic modulus of 1000 MPa or more in the optical cable slot 2 is preferably 60% by mass, more preferably 70% by mass, and even more preferably 75% by mass. When the content of the resin is less than 50% by mass, there is a possibility that the crushing strength of the optical cable slot 2 and the effect of suppressing waviness during bending cannot be sufficiently obtained.

The optical cable slot 2 may contain components other than the resin having a pressure of 1000 MPa or more. Other components include resins other than resins having a pressure of 1000 MPa or more and various additives. The upper limit of the content of other components is preferably 5% by mass, more preferably 1% by mass, and even more preferably substantially free of other components.

The optical cable slot 2 has a groove formed by the surfaces of the adjacent ribs 21, and the optical fiber 4 is disposed in this groove. FIG. 2 shows an example in which eight optical cable slots 2 are provided. As shown in FIG. 3, the groove of the optical cable slot 2 is spirally formed. Moreover, as shown in FIG. 3, the groove of the optical cable slot 2 of the optical cable slot 2 is formed in a spiral shape. Further, the shape of the groove formed by the adjacent ribs 21 in a cross-sectional view can be, for example, V-shaped, rectangular, U-shaped, fan-shaped, or the like. As shown in FIG. 2, in this embodiment, the shape of the groove is a sector.

(rib)
The rib 21 has a shape that protrudes from the peripheral surface of the main body of the slot 2 . The rib 21 is spirally provided on the outer peripheral surface in the axial direction. Each rib 21 has a band shape and is integrally formed with the main body 24 so that the inner edge in the longitudinal direction is helically joined to the main body 24. Each rib 21 has a band shape and is integrally formed with the main body 24 so that the inner edge in the longitudinal direction is helically joined to the main body 24.

A slot 2 groove is formed between adjacent ribs 21, and is separated from other optical cable slots 2. That is, the groove of the optical cable slot 2 is a groove between adjacent ribs 21. The optical fiber 4 is arranged in a groove formed between adjacent ribs 21.

The twisting pitch of the ribs is preferably 600 mm or more and 1600 mm or less, more preferably 600 mm or more and 800 mm or less. By setting the twisting pitch of the ribs to be 600 mm or more and 1600 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs.

The average height h1 of the ribs 21 is preferably 5 mm or more and 30 mm or less, and more preferably 6 mm or more and 25 mm or less. By setting the average height h1 of the ribs 21 to be 5 mm or more and 30 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs 21.

The above-mentioned "average height h1 of the ribs 21" refers to the average value of the heights measured by the following procedure. FIG. 4 is a partial schematic diagram of the slot 2 for explaining the average height h1 of the rib 21. As shown in FIG. 4, first, a straight line connecting two points L1 and L2 located at the lowest points of adjacent grooves via an arbitrary rib 21 is set. If this straight line is the base, the average height of the perpendicular line connecting the base and the apex of the rib 21 is the average height h1.

The average thickness t of the ribs 21 is preferably 0.5 mm or more and 5.0 mm or less, and more preferably 0.5 mm or more and 3 mm or less. By setting the average thickness t of the ribs 21 to be 0.5 mm or more and 3 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the ribs 21.

The ratio h1/t of the average height h1 to the average thickness t in the rib 21 is 4 or more, more preferably 5 or more. When the ratio h1/t of the average height h1 to the average thickness t in the rib 21 is 4 or more, the rib 21 can be made thinner. By making the ribs 21 thinner, optical fibers can be accommodated at a higher density.

(slit)
The rib has a plurality of slits 25 extending in the axial direction from the outer edge in the longitudinal direction. The plurality of slits 25 are arranged at intervals in the longitudinal direction of the rib 21. The slit 25 is open toward the outer edge in the longitudinal direction, and as shown in FIG. 4, the slit 25 extends substantially perpendicularly inward from the outer edge in the longitudinal direction of the rib 21 in plan view.

The ratio h2/h1 of the average depth h2 of the slits 25 to the average height h1 of the ribs 21 is 0.5 or more and 0.8 or less, and preferably 0.6 or more and 0.8 or less. By setting the ratio h2/h1 of the average depth h2 of the slits 25 to the average height h1 of the ribs 21 to be 0.5 or more and 0.8 or less, appropriate elasticity can be imparted while maintaining the crushing strength of the ribs. I can do it.

It is preferable that the ribs 21 have at least one slit per pitch, and more preferably four or more slits per pitch. Since the ribs 21 have at least one slit per pitch, the crushing strength of the ribs 21 can be maintained and the effect of suppressing waviness during bending can be enhanced.

The average width w1 of the slit 25 is preferably 0.1 mm or more and 20 mm or less, more preferably 2 mm or more and 18 mm or less. By setting the average width w1 of the slits 25 to 0.1 mm or more and 20 mm or less, the effect of suppressing waviness during bending can be enhanced while maintaining the crushing strength of the rib.

(Tension member)
In order to prevent the optical cable 11 from stretching due to its own weight during installation, a tension member 1 that bears tension is arranged at the center. If the optical cable slot and the tension member are not firmly adhered, they will shift during installation, and only the optical cable slot will stretch, which will put tension on the optical fiber and cause worsening of transmission loss and disconnection. As the tension member 1, for example, a single or twisted metal wire, a linear body made of organic or inorganic fiber, etc. can be used.

(optical fiber)
As the optical fiber 4, a known optical fiber can be used. For example, a tape core in which a plurality of optical fiber cores are bundled with a coating can be suitably used, but a single optical fiber core may also be used. Note that when a tape core wire is used as the optical fiber 4, the optical cable 11 becomes a so-called tape slot type optical cable.

(outer covering)
The jacket 5 is a resin layer that covers the optical cable slot 2 and the outer periphery of the optical fiber 4. The main component of the outer sheath 5 is not particularly limited, and for example, polyethylene or the like is used. Note that the outer cover 5 may have a multilayer structure having multiple types of layers.

[Optical cable manufacturing method]
Next, an example of a method for manufacturing the optical cable will be described. The optical cable manufacturing method includes, for example, a step of manufacturing an optical cable slot, a step of assembling the optical cables, and a step of covering the outer jacket.

In the step of manufacturing an optical cable slot (optical cable slot manufacturing step), the optical cable slot is formed, for example, by profile extrusion of a resin composition constituting the optical cable slot. Specifically, the tension member and the heated resin composition are extruded through a die to form an optical cable slot that covers the tension member. At this time, by rotating the die during extrusion, a plurality of ribs are spirally erected in the axial direction on the outer peripheral surface of the optical cable slot.

Note that the optical cable slot can be manufactured not only by extrusion molding but also by injection molding, compression molding, or the like. A cutting machine is used to press blades against the obtained slots at regular intervals from the longitudinal outer edge of the rib toward the axial direction to form slits. Here, the depth and width of the slit can be adjusted by changing the length and thickness of the blade that is pressed against it.

In the step of gathering optical cables (gathering step), the optical fibers are gathered by entering the grooves of the optical cable slots formed in the optical cable slot manufacturing step and winding them under pressure.

In the step of covering the outer sheath, the outer periphery of the assembly of the optical cable slot and the optical fiber obtained in the assembling step is covered with the outer sheath. As this coating method, for example, extrusion molding or the like is used.

According to the optical cable slot, by making the ribs thinner, it is possible to increase the capacity of optical fibers, and the crushing strength of the ribs and the effect of suppressing waviness during bending of the optical cable are excellent.

According to the optical cable, since the optical cable slot of the present disclosure is provided, the rib in the optical cable slot can be made thinner, and the crushing strength of the rib and the effect of suppressing waviness when bending the optical cable are excellent.

[Other embodiments]
The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the embodiments described above, but is indicated by the claims, and is intended to include all changes within the meaning and range equivalent to the claims. Ru.

EXAMPLES Hereinafter, the present disclosure will be explained in more detail with reference to Examples, but the present disclosure is not limited to the following Examples.

<Test No. 4~Test No. 6>
A slot made of 100 parts by mass of polypropylene (Novatec PP EA9FTD, manufactured by Nippon Polypro Co., Ltd.) having a flexural modulus of 1800 MPa was molded and coated on the outer peripheral surface of a metal tension member.

The flexural modulus of the resin used as the material of the slot was measured using a tensile tester in accordance with JIS-K-7171 (2016).

The slots were made by heating resin to 180° C. and extrusion molding it. Regarding the shape of the ribs, the average rib height h1 was 24 mm, the average rib thickness t was 3 mm (thin type), and the ratio h1/t of the average rib height to the average rib thickness was 8. Further, the spirally provided slot shape was twisted in one direction, with one pitch (twisting pitch) of 600 mm. The ribs include slits having an average slit depth h2, a ratio h2/h1 of the average slit depth h2 to the average rib height h1, an average slit width w1, and the number of slits per pitch as shown in Table 1. Formed.

<Test No. 3>
Test No. except that no slit was formed in the rib of the slot. A slot was molded in the same manner as in 4 and coated on the outer peripheral surface of the tension member.

<Test No. 2>
Test No. 1 was used except that 100 parts by mass of polyethylene ("Nipolon LF13" manufactured by Tosoh Corporation) having a bending modulus of elasticity of 800 MPa was used as the material for forming the slots, and no slits were formed in the slots. A slot was molded in the same manner as in 4 and coated on the outer peripheral surface of the tension member.

<Test No. 1>
Test No. 1 was used except that the rib shape of the slot was such that the average rib height h1 was 24 mm, the average rib thickness t8 mm (conventional product type), and the ratio h1/t of the average rib height to the average rib thickness was 3. A slot was molded in the same manner as in 2 and coated on the outer peripheral surface of the tension member.

<Evaluation>
Test No. 1 includes the fabricated tension member and slot. 1~Test No. The following evaluations were performed on the test specimen No. 6. These results are shown in Table 1.

(Waviness evaluation)
After wrapping the optical cable slot in two layers around a drum with a radius of 10D (D: diameter of the optical cable slot) mm at a tension of 500N, the presence or absence of waviness in the ribs was visually confirmed. If undulations were observed in the ribs, the product was judged to have failed.

(Crushing strength test)
The top and bottom of the slot are sandwiched between two 100mm square stainless steel plates with an average thickness of 10mm, and a load is applied using a compression tester.The load that causes deformation of the rib is defined as the crushing strength, and 2200N or more is considered A (pass). If it was less than that, it was rated B (fail).

(Occupancy rate of optical fiber in cable)
Regarding the density of optical fibers in a cable, the total cross-sectional area of all the optical fibers housed in the space surrounded by the two ribs and the jacket is divided by the cross-sectional area of the space surrounded by the two ribs and the jacket. The value was taken as the optical fiber occupancy, and the occupancy of 0.4 or more was rated A, and the occupancy of less than 0.4 was rated B.

As shown in Table 1, the bending elastic modulus of the material resin is 1000 MPa or more, the ratio h1/t of the average height h1 to the average thickness t in the rib of the slot is 4 or more, and the ratio h1/t to the average height h1 of the rib is 4 or more. Test No. in which the ratio h2/h1 of the average depth h2 of the slit is 0.5 or more and 0.8 or less. 4.No. 6 and no. In No. 7, the crushing strength of the ribs was excellent, and no waviness was observed in the evaluation of the waviness of the ribs after being wound around the drum. Test No. 4.No. 6 and no. Test No. 7 is a reference example of a conventional product type having thick ribs (h1/t less than 4) whose resin material has a bending modulus of 800 MPa. It can be seen that the density of the optical fiber can be improved while having the same crushing strength as No. 1.

On the other hand, the reference example test No. Test No. 1 was prepared in which the ribs of No. 1 were made thinner, the bending elastic modulus of the material resin was 800 MP, and there were no slits. In No. 2, no undulations occurred in the ribs even when wrapped, but the crushing strength of the ribs was poor. Test No. 1 has thin ribs, the bending elastic modulus of the resin material is 900 MP, and has no slits. In No. 3, undulations occurred in the ribs when wrapped, and the crushing strength was poor.
Also, test no. As shown in Fig. 5, even if the bending elastic modulus of the resin material was 1000 MPa or more, when the thin ribs did not have slits, undulations occurred when the ribs were wound. Furthermore, test no. As shown in Fig. 8, even if a thin rib whose resin material has a bending modulus of elasticity of 1000 MPa or more has slits, when h2/h1 is less than 0.5, undulations occur when the rib is wrapped. Test No. in which h2/h1 exceeds 0.8. In No. 9, the crushing strength of the rib was poor.

The above results showed that the optical cable slot allows the rib to be made thinner, has a high crushing strength, and has an excellent effect of suppressing the waviness of the rib when bending the optical cable.

By making the ribs thinner, the optical cable slot can accommodate an increased amount of optical fibers, and the ribs have excellent crushing strength and an effect of suppressing waviness during bending of the optical cable. Therefore, the optical cable provided with the optical cable slot can be suitably used for wiring between data centers where a large amount of information is transmitted or between floors of data centers.

1 Tension member 2 Optical cable slot 4 Optical fiber 5 Outer jacket 11 Optical cable 21 Rib 22 Slot center 24 Slot main body 25 Slit

Claims (5)

Contains a resin with a bending modulus of 1000 MPa or more,
It has a plurality of ribs provided spirally in the axial direction on the outer peripheral surface,
The ratio h1/t of the average height h1 to the average thickness t in the rib is 4 or more,
The rib has a plurality of slits extending in the axial direction from the outer edge in the longitudinal direction,
A slot for an optical cable, wherein a ratio h2/h1 of an average depth h2 of the slit to an average height h1 of the rib is 0.5 or more and 0.8 or less. The optical cable slot according to claim 1, wherein the twisting pitch of the ribs is 600 mm or more and 1600 mm or less. The optical cable slot according to claim 1 or 2, wherein the average width of the slit is 0.1 mm or more and 20 mm or less. 3. The optical cable slot according to claim 1, wherein the rib has at least one slit per pitch. An optical cable slot according to claim 1 or 2;
a tension member buried in the center of the slot;
an optical fiber disposed between the adjacent ribs;
An optical cable comprising: an outer sheath that covers the slot and the optical fiber.

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